1. Technical Field
The present invention relates to a common mode filter, and more particularly, to a structure of a coil electrode pattern in a common mode filter.
2. Description of the Related Art
In accordance with the development of a technology, electronic devices such as a portable phone, a home appliance, a personal computer (PC), a personal digital assistant (PDA), a liquid crystal display (LCD), and the like, have been changed from an analog scheme into a digital scheme and a speed of the electronic devices has increased due to an increase in an amount of processed data. Therefore, a universal serial bus (USB) 2.0, a USB 3.0, and a high-definition multimedia interface (HDMI) have been widely spread as a high speed signal transmitting interface and have been used in many digital devices such as a personal computer and a digital high-definition television.
These interfaces adopt a differential signal system transmitting differential signals (differential mode signals) using a pair of signal lines unlike a single-end transmitting system that has been generally used for a long period of time. However, electronic devices that are digitized and have an increased speed are sensitive to stimulus from the outside. That is, in the case in which a small abnormal voltage and high frequency noise are introduced from the outside into an internal circuit of the electronic device, a circuit may be damaged and a signal may be distorted.
In order to prevent the damage to the circuit of the electronic device and generation of the signal distortion, a filter is installed to prevent the high frequency noise from being introduced into the circuit. Generally, a common mode filter has been used in a high speed differential signal line, or the like, in order to remove common mode noise.
The common mode noise indicates noise generated in the differential signal line, and the common mode filter removes noise that may not be removed by an existing electromagnetic interference (EMI) filter. The common mode filter contributes to improvement in EMI characteristics of a home appliance, or the like, and improvement of antenna characteristics of a cellular phone, or the like.
Referring to Japanese Patent Laid-Open Publication No. 2012-015494, a general common mode filter according to the related art includes a metal-polymer composite filled around first and second coil electrode patterns enclosed by an insulating resin.
Here, the first and second coil electrode patterns are stacked while having the insulating resin therebetween in order to enhance electromagnetic coupling therebetween. Therefore, the first and second coil electrode patterns are disposed to face each other in a vertical direction.